docs: def main(args):
      '''
      register_retinotopy.main(args) can be given a list of arguments, such as sys.argv[1:]; these
      arguments may include any options and must include at least one subject id. All subjects whose
      ids are given are registered to a retinotopy model, and the resulting registration, as well as
      the predictions made by the model in the registration, are exported.
      '''
      m = register_retinotopy_plan(args=args)
      # force completion
      files = m['files']
      if len(files) > 0:
          return 0
      else:
          print('Error: No files exported.', file=sys.stderr)
          return 1